Which of the following equations demonstrate that the set of polynomials not closed under the certain operations

Carl wants to buy a television that cost $500 including taxes. to pay for television he will use a payment plan that requires him to make a down payment of $125 and then pay $70.50 each month for six months what is the percent increase from the original cast of the television to the cost of the television using a payment plan.

Write the equation for the parabola that has x− intercepts (−2,0) and (4,0) and y− intercept (0,4).

Find the center and the radius of the circle with the equation: x^2-2x+y^2+4y+1=0?